Vacuum packaging is a well known process for packaging a wide variety of products, in particular food products. Among the known vacuum packaging processes, vacuum skin packaging is commonly employed for packaging food products such as fresh and frozen meat and fish, cheese, processed meat, ready meals and the like. Vacuum skin packaging is described for instance in FR 1 258 357, FR 1 286 018, AU 3 491 504, US RE 30,009, U.S. Pat. No. 3,574,642, U.S. Pat. No. 3,681,092, U.S. Pat. No. 3,713,849, U.S. Pat. No. 4,055,672, and U.S. Pat. No. 5,346,735.
Vacuum skin packaging is basically a thermoforming process. In particular, the product is typically placed on a rigid or semi-rigid support (such as a tray, a bowl or a cup). The support with the product placed thereon is put in a vacuum chamber, where a film of thermoplastic material, held by vacuum in a position above the product placed on the support, is heated to soften it. The space between the support and the film is then evacuated and finally vacuum above the film is released to cause the film to drape down all around the product and seal to the surface of the support not covered by the product, thus forming a tight skin around the product and on the support.
US 2007/0022717 discloses a machine for gastight packaging an object using a film material. The machine has a lower tool for supporting two trays and an upper tool having cutting devices and facing the lower tool. A film is interposed between the upper tool and the lower tool. The film is firstly cut to the size of the peripheral rims of the trays, and is applied subsequently and/or simultaneously to the peripheral rim in a gastight manner. A vacuum is situated in the surrounding region of the tray to cause deep-drawing of the film in response to the formation of a pressure drop.
US 2005/0257501 discloses a machine for packaging a product arranged in a tray. The machine has a lower tool for supporting the tray and an upper tool with a cutting device. During operation, the film is clamped along an edge surrounding the tray and is deformed by the upper tool in a direction extending away the product. The space surrounding the product is then evacuated, the film and the edge of the tray are sealed and the film is then cut by the cutting device.
U.S. Pat. No. 3,481,101 discloses a method for making skin packages using a support provided with a plurality of apertures in a lip thereof. According to this method, after the tray is filled, a heated cover film is draped upon the tray and vacuum is applied so that the air within the package is drawn from the package and the film is drawn into heat sealing condition with the tray to form a hermetic seal of the cover to the tray lip. Additional apertures may be provided in the upper sidewalls of the tray whereupon the heated film is not only drawn into sealing contact with the lip of the tray, but also is drawn down partially into the cavity.
EP 320294 discloses a skin packaging method wherein a product loaded tray provided with a vent in its sidewall is placed on a vacuum platen, an excess of the thermoplastic film is held over the tray by a frame and heated until it starts to sag over the product, then vacuum is applied from below the tray to pull the film to conform to the surface of the product and over and around the rim of the tray in a thermally set crimp seal. The excess film is then trimmed.
In most of the above solutions, removal of air from the interior of the support tray is possible only as long as the film is held above the support tray and the product. As soon as the film contacts and seals the top edge of the tray, air can no longer be removed from within the tray. Thus, particularly when a deep tray is used as a support for the product, air pockets may disadvantageously remain entrapped between the film and the bottom surface of the support. These air pockets may negatively influence the shelf-life of the product as well as the impression that the consumer has of the package.
In the skin packaging methods of U.S. Pat. No. 3,481,101 and EP 0320294, the apertures provided in the support tray allow removal of air from within the support even after the film has contacted the support tray, thus reducing the risk of leaving air pockets in the package. Although these solutions have improved the capability of removal of air from within the tray, the packaging methods described in U.S. Pat. No. 3,481,101 and EP 0320294 require use of suitably designed trays. This implies a certain burden in the production chain. Moreover, the position or size of the holes or venting channels present on the tray may not be always optimized to the specific packaging machine. Additionally, the presence of holes on the tray walls causes an undesirable aesthetic perception of the overall packaging.
Trays with pre-manufactured holes are known from U.S. Pat. No. 4,919,955, WO9714313 and US2005074531. The holes present on the trays disclosed in U.S. Pat. No. 4,919,955 and US2005074531 are provided with a valve means.
It is therefore an object of the present invention to provide an apparatus and a method capable of adequately solving the problem of air removal from the tray, without impairing in term of overall packaging costs.
Moreover, it is an auxiliary object providing a method and an apparatus which are capable of efficiently remove air from the tray during packaging.
Additionally, it is an object providing a method and an apparatus which may be implemented with no need of complex changes to conventional packaging systems.
Another auxiliary object is an apparatus capable of operating in a safe manner.
A further auxiliary object is an apparatus and a method capable of achieving the goal of air removal without impairing on the aesthetics of the final packaged product.
Another object of the invention is a new package having a design allowing efficient air removal and improving the aesthetic perception of the package.